1. Field of the Invention
The present invention relates to a mobile information terminal, and particularly to a mobile information terminal executing application programs.
2. Description of the Prior Art
In recent years, mobile phones have had improved functions, making them usable as radios, audio apparatuses, game consoles, and the like. In order to operate mobile phones as radios, audio apparatuses, game consoles, and the like, the central processing units mounted in the mobile phones execute various application programs. However, there are cases where the central processing units run away due to bugs in application programs or unexpected operations. When the central processing unit runs away, it cannot reset itself. Thus, when power is operated by monitoring using software, even disconnection of power is impossible. Although the runaway can be prevented by clearing a watch dog timer mounted in the central processing unit, this method is not effective in the case where the central processing unit runs away while clearing the watch dog timer. In these cases, there has been no way to stop the runaway but to cut off power supplied to the central processing unit by, for example, removing the battery, which is mounted as the power source for the mobile phone.
Japanese Patent Application Publication No. 5-3005 describes a resetting device to reset a computer using a resetting switch. The resetting device includes a resetting switch, an interruption-demand-signal outputting portion to, in response to a resetting signal from the resetting switch, output to the computer an interruption demand signal for interrupting a computer system in order to cause the computer system to execute a software resetting operation, a trigger signal outputting portion to output a trigger signal when the resetting signal lasts for a predetermined period of time, and a resetting signal outputting portion to, in response to the trigger signal, output a hardware resetting signal to the computer system in order to cause the computer system to execute a hardware resetting operation.
However, when the computer is reset while an application program is being executed without runaway of the central processing unit, data that has been processed so far in the central processing unit can be lost, or the application program can be discontinued without writing data that has been set. This causes failure of the program which cannot be booted normally the next time power is supplied.